A load raising and lowering

ABSTRACT

A load raising and lowering apparatus includes a load-supporting platform which is suspended on a pair of chains and is movable between an extreme upper and an extreme lower position. The pair of chains are positioned about an upper pair of sprockets and a lower pair of sprockets. The two ends of each chain are connected to the platform. The upper end of each chain is directly connected to respective sides of the platform. The lower end of each chain is connected, via respective springs, to the respective sides of the platform at points below those points to which the respective upper ends of the chains are connected. The spring constants of the springs are at least approximately equal to the spring constants of the respective chains.

United States Patent Grebenstein Mar. 12,' 1974 [54] LOAD RAISING AND LOWERING 2,808,126 10/1957 Harrer l87/20 [75] Inventor: Hermann Grebenstein,

UnteFEl-Hmbach, Switzerland Primary Examiner-Richard A. Schacher Attorney, Agent, or Firm-Edwin E. Greigg [73] Ass1gnee: Oehler-, Wyhlen-Lagertechnik AG, Aarau, Switzerland [57] ABSTRACT [22] Filed: July 6, 1972 A load ra1s1ng and lowermg apparatus mcludes a loadl l pp N05 269,464 supporting platform which is suspended on a pair of chains and is movable between an extreme upper and [30] Foreign Application Priority Data an exrerlraie lower position. Th; pair 0; cthainsdarelposihome a out an upper pan 0 sproc e s an a ower July 14, 1971 Switzerland 10450/71 p of sprockets The two ends of each chain are con nected to the platform. The upper end of each chain is CCll. dimcfly connected to respective sides of the platform. [58] Fieid 12 2O 27 The lower end of each chain is connected, via respective springs, to the respective sides of the platform at [56] References Cited points below those .points to which the respective upper ends of the chains are connected. The spring UNITED STATES PATENTS constants of the springs are at least approximately 657,380 .9/l900 Baldwin 187/20 equal to the spring onstants of the respective chains 1,312,089 8/1919 Anderson.... 3,592,294 7/1971 Allen 187/12 1 Claim, 1 Drawing Figure A LOAD RAISING AND LOWERING The present invention relates to a device for the raising and lowering of loads with a load-carrying element displaceable in vertical direction, which is Suspended on either side by means of at least one circulating supporting and guiding element, the direction of which is reversed in the region of the upper and lower extreme position of said load-carrying element, a spring being inserted in each of the support and guiding elements.

The handling capacity of load-moving devices, in particular of warehousing machines in high-shelf storage facilities, is heavily dependent upon the speed of movement and upon factors influencing acceleration and deceleration in lifting and travelling. With increasing height of the lift and rising speed in the horizontal direction, the effect of movements during acceleration and deceleration increases sharply, and this, together with the unevennesses of the path resulting from the mechanical tolerances, lead to irregular, dynamic behaviour on the part of the warehousing machine.

Particularly in the case of lifting heights of 25 m and more, such disturbances of the dynamic behaviour can produce oscillations of the entire load-handling device and especially of the ropes or chains by means of which the platform carrying the load is suspended. Oscillations of this type are greatly feared, as they can result in a shifting of the load, which makes it difficult to position the entire load-handling device accurately. Such load shifting is especially undesired in the case of goods stored on pallets, and this can compel the imposition of disadvantage limitations on the speed of movement in order to avoid malfunctions in the storage facility, which is frequently operated fully automatically.

For these reasons the proposal has been made in the past to secure all loads to the pallets with metal straps or other fastening elements. This proposal is usually not feasible in actual practice, however, since the stored goods often have to remain accessible in their individual parts, such as for the filling of orders.

The load-carrying platform is usually suspended from steel ropes or chains and provided with an automatically-functioning safety apparatus. For such load-handling devices with great lifting height, the danger exists that irregular changes in stress, especially but not only the reversal of direction of the drive unit, will cause the ropes or chains to oscillate freely. The object of the present invention is to prevent such oscillations effectively and thus to prevent with certainty a shifting of the load. According to the invention, this is achieved for a device for the raising and lowering of loads of the type mentioned above through the fact that the spring constants of the springs are at least approximately equal to the spring constants of the support and guiding elements.

In connection with this it has proven to be of advantage if the guiding and driving elements, which for example can consist of chains, are placed under initial tension by means of the springs. Each of these chains can be passed over a pair of sprockets, whereby the two lower sprockets are advantageously coupled together and connected to a drive unit. It is further of advantage for the direct connection between chain and load-carrying element is made at the upper end of said element, while the lower end is connected to the chain via the spring.

' in the area of the other side wall 2 of the platform 1 is passed over an upper sprocket 8 and a lower sprocket 9, which can be coupled together. The upper end of the chain 7 is attached directly to a point 11 on the side wall 2. A spring 12 serves to connect the lower end of the chain 7 with the side wall 2. The chain 4 is attached to the side wall 3 in the same manner. Both of these chains are placed under initial tension so that the springs are in the stressed condition in the position of rest.

The spring constants of the two springs are chosen to be at least approximately equal to the spring constants of the two chains 4 and 7. Since the chains 4 and 7 do not act as rigid bodies, but rather undergo elastic de formation under stress, this means that, when subjected to a given force, the length of the two springs changes by the same amount as does the length of the two similarly stressed chains 4 and 7. The result of this is that the tension between the suspension points of the load, i.e. between point 11 and the corresponding points on the side wall 3 on the one hand and points 14 and 15 respectively on the periphery of the lower sprockets 6 and 9 is constant and independent of the load on the platform 1. This measure serves to suppress oscillation of the chains with certainty. A further advantage of this arrangement lies in the fact that the drive shaft 13 for the sprockets can be located at the bottom, which considerably reduces the top-heaviness ofa load-handling device which is also movable in the horizontal direc tion. It also affords better accessibility to the drive elements, which means a significant time saving in maintenance and repair work.

What I claim is:

l. A load raising and lowering apparatus for moving a load between a lower extreme position and an upper extreme position comprising, in combination:

a. a pair of first sprockets arranged for rotation about a first axis above and in the vicinity of the upper extreme position;

b. a pair of second sprockets arranged for rotation about a second axis below and in the vicinity of the lower extreme position;

c. a pair of suspension chains, free of counterweights, each having upper and lower ends, each having a spring constant, and each being respectively positioned about one sprocket of each of said pairs of sprockets; 1

d. a platform for supporting the load and having two spaced apart sides, said upper end of each of said chains being connected directly to respective ones of said sides at respective first points thereon; a pair of springs which place said chains under initial tension, each spring having a first end connected directly to a respective different one of said sides at respective second points below said first points thereon, each spring having its second end connected to a respective different one of said lower ends of said chains, and each spring having spring constants which are at least approximately equal to the spring constants of said chains; whereby oscillations are substantially prevented by damping. 

1. A load raising and lowering apparatus for moving a load between a lower extreme position and an upper extreme position comprising, in combination: a. a pair of first sprockets arranged for rotation about a first axis above and in the vicinity of the upper extreme position; b. a pair of second sprockets arranged for rotation about a second axis below and in the vicinity of the lower extreme position; c. a pair of suspension chains, free of counterweights, each having upper and lower ends, each having a spring constant, and each being respectively positioned about one sprocket of each of said pairs of sprockets; d. a platform for supporting the load and having two spaced apart sides, said upper end of each of said chains being connected directly to respective ones of said sides at respective first points thereon; e. a pair of springs which place said chains under initial tension, each spring having a first end connected directly to a respective different one of said sides at respective second points below said first points thereon, each spring having its second end connected to a respective different one of said lower ends of said chains, and each spring having spring consTants which are at least approximately equal to the spring constants of said chains; whereby oscillations are substantially prevented by damping. 